Although they forbid annotating subject and predicate as a coreferent pair, ON guidelines do specify a hierarchy for determining which of the two should be taken as the antecedent for subsequent mentions, ranking names above pronouns, and pronouns above definite NPs. These kinds of configurations therefore appear in the official CoNLL coreference shared task dataset and consequently model the output that contemporary coreference resolution systems attempt to produce. I will leave it to readers to imagine scenarios in which the missing member of the chain will lead to loss of information,See also [1]} for an example. but suffice it to say that including them would not lead to the scope problems above; in fact, some corpora already separate indefinite predication from regular coreference such as ARRAU [2]} and GUM, which treat identificational predication as regular coreference, and either label predicative markables whenever semantically applicable (ARRAU), or maintain a special coreference relation subtype for non-identificational cases (GUM, see Appendix).
